DIDEOXY FINGERPRINTING FOR RAPID SCREENING OF RPOB GENE-MUTATIONS IN CLINICAL ISOLATES OF MYCOBACTERIUM-TUBERCULOSIS

Rifampin is a key component of therapeutic regimens for tuberculosis c ontrol, and a market for multidrug resistance of Mycobacterium tubercu losis. Mutations responsible for conferring rifampin resistance in M. tuberculosis are known to occur in a 69-bp region of the rpoB gene. In this study we assessed the accuracy of dideoxy fingerprinting (ddF), a hybrid technique employing elements of dideoxy sequencing and single -strand polymorphism analysis, for rapid screening of rifampin resista nce in clinical isolates of M, tuberculosis. This technique was used t o analyze 72 M, tuberculosis isolates. The results were compared with those of automated dideoxy sequencing and the antibiotic resistance pr ofile (determined with the BACTEC system). Of the 72 isolates, 50 were rifampin resistant. The ddF findings were completely consistent with those of dideoxy sequencing in all isolates. In 68 (94%) isolates, the ddF findings were consistent with the rifampin resistance status dete rmined with the BACTEC system; all four isolates with inconsistent res ults had no mutation in the 69-bp region, but were resistant to rifamp in. Our findings suggest that ddF accurately detects mutations in the rifampin resistance-associated 69-bp region of the rpoB gene in clinic al isolates of M. tuberculosis and may be a valuable screening tool fo r rifampin resistance.